rivet-rmgaps: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/rivet-rmgaps - from package: rivet

You may install the required package with command apt-get install {package}

Error in other languages:
rivet-rmgaps: bevel nie gevind nie
rivet-rmgaps: comandă negăsită
rivet-rmgaps: comando não encontrado
rivet-rmgaps: commande introuvable
rivet-rmgaps: command not found
rivet-rmgaps: käsku ei ole
rivet-rmgaps: không tìm thấy lệnh
rivet-rmgaps: komanda nerasta
rivet-rmgaps: Kommando nicht gefunden.
rivet-rmgaps: kommandot finns inte
rivet-rmgaps: komut yok
rivet-rmgaps: nie znaleziono polecenia
rivet-rmgaps: níor aimsíodh an t-ordú
rivet-rmgaps: no se encontró la orden
rivet-rmgaps: no s'ha trobat l'ordre
rivet-rmgaps: opdracht niet gevonden
rivet-rmgaps: parancs nem található
rivet-rmgaps: perintah tidak ditemukan
rivet-rmgaps: príkaz nenájdený
rivet-rmgaps: příkaz nenalezen
rivet-rmgaps: команда не найдена
rivet-rmgaps: командата не е открита
rivet-rmgaps: 命令找不到
rivet-rmgaps: コマンドが見つかりません